Jerky braking

[Royalstorm]

Hi guys,
I actually am back on again for a similar issue that I posted about back in 2018 for my previous ’18 Stinger GT base regarding engine braking and jarring deceleration. I recently traded the ’18 for a 2022 GT2. Overall happy with the upgrades but am finding the braking far more bothersome compared to my 2018 GT base. Over time I got used to the engine braking in Sport Mode on the ‘18. But with the GT2 I find it much more jarring in Sport Mode with an almost jerky sensation after each auto-downshift. When applying the brakes going around 50 mph, I can feel the engine grab during the downshift with immediate deceleration but it’s almost as if the clutch is then disengaging and the car “slips” with less grab and then the engine grabs again. This happens all within a second so it feels like a lurching sensation. With my 2018, the car would abruptly decelerate when the downshift occurred but it remained consistent until the next downshift when it would again decelerate more aggressively. I have put the car in comfort mode and its definitely less noticeable, so I assume it’s just the programming but could there a transmission component to it as well that’s off?

 

[JSolo]

How many miles on the car? My 2.5T smoothed out quite a bit with a few thousand miles. 4K now and reasonably smooth when braking. I don't use sport mode unless I need it. I think it will be more abrupt by design in sport mode as the intention is to keep the rpms higher meaning lower gear for a given speed. Lower gear means more engine braking.

 

[MerlintheMad]

You got the GT1 taken back?

 

[Royalstorm]

How many miles on the car? My 2.5T smoothed out quite a bit with a few thousand miles. 4K now and reasonably smooth when braking. I don't use sport mode unless I need it. I think it will be more abrupt by design in sport mode as the intention is to keep the rpms higher meaning lower gear for a given speed. Lower gear means more engine braking.

It only has 650 miles on it. Totally agree with the engine braking. It just seems different than my ‘18. Right after the downshift, car decelerates for a split second then almost “releases “ and then catches again, so it’s not a smooth aggressive deceleration (like I had in the ‘18) but a jerky sensation (like you would expect applying the brakes hard for a split second, then letting off, and then reapplying again all within rapid succession). Hopefully it will smooth out over time.

 

[Royalstorm]

You got the GT1 taken back?

Taken back is probably generous though I traded it in and got a new gt2 below invoice so it was close to a wash. Just felt like I was sitting on a ticking time bomb of repetitive problems as the dealership was so shady about the problems. May have been fine in the long run but I’m just too OCD to relax and enjoy it (surprising I know, as here I am posting another question)….

 

[SRV]

It does take getting used to, but you'll learn and not even think about it after a while.

 

[Royalstorm]

So if you are driving around 60 mph and apply the brakes firmly, is there fairly uniform deceleration? For me, there are at least 2-3 “blips” where it’s really uneven for a brief second during each downshift. With my old car, I remember each down shift being aggressive but still smooth, if that makes sense. This is very different. I’ve looked up the description of rotor warping but that doesn’t seem to fit either as it’s less intense in comfort mode. Is there any chance that the transmission could be partially disengaging after each downshift for a brief second and then reengaging?

 

[Royalstorm]

I finally eclipsed the 600 mile mark and am pushing her a bit more. I even tried “seating” the brakes based on other forums but doesn’t seem to have helped.

When driving last night I also noticed that when cruising around 45-50 in sport mode at around 2000 rpm, when I accelerate moderately, the boost kicks in and acceleration is also a bit juddery. If the car downshifts, acceleration seems pretty uniform but if it remains in a lower gear, it’s not smooth. Is this engine lugging? Again, I never experienced this in my 2018 GT. No matter how I accelerate, boost and acceleration were uniform and smooth. I’m going to have my dealership look at it next week to get their opinion but curious if anyone else has experienced similar inconsistent acceleration.

 

[MerlintheMad]

diebshidts

Eh? Fingers on the right keys works well.

I’m going to have my dealership look at it next week to get their opinion but curious if anyone else has experienced similar inconsistent acceleration.

Sounds like a bad plug/coil issue. That's what my "juddery" acceleration was.

 

[JSolo]

^^downshits?

 

[Royalstorm]

Eh? Fingers on the right keys works well.

Sounds like a bad plug/coil issue. That's what my "juddery" acceleration was.

If it is a bad coil, would you expect more severe juddering as rpms climb? I notice it only if car remains in a higher gear as rpms climb during turbo boost. If car downshits (intentional this time), acceleration seems smoother with the higher rpms.

 

[MerlintheMad]

If it is a bad coil, would you expect more severe juddering as rpms climb? I notice it only if car remains in a higher gear as rpms climb during turbo boost. If car downshits (intentional this time), acceleration seems smoother with the higher rpms.

If I avoided boost the engine ran smoothly at any speed. The bad boot/coil kept ruining replacement plugs.

 

[CKeeler]

My ‘18 has done it since new. 57k now. So annoying. Even though I know what it is, I keep thinking it’s warped brakes.

 

[Scorpion24]

I finally eclipsed the 600 mile mark and am pushing her a bit more. I even tried “seating” the brakes based on other forums but doesn’t seem to have helped.

When driving last night I also noticed that when cruising around 45-50 in sport mode at around 2000 rpm, when I accelerate moderately, the boost kicks in and acceleration is also a bit juddery. If the car downshifts, acceleration seems pretty uniform but if it remains in a lower gear, it’s not smooth. Is this engine lugging? Again, I never experienced this in my 2018 GT. No matter how I accelerate, boost and acceleration were uniform and smooth. I’m going to have my dealership look at it next week to get their opinion but curious if anyone else has experienced similar inconsistent acceleration.

Did the dealer figure out what it was? I have a 22 with similar experiences in sport mode.

 

[Royalstorm]

Did the dealer figure out what it was? I have a 22 with similar experiences in sport mode.

So they couldn’t find any codes when they plugged it in but decided to reset the adaptive values for the engine and transmission. I haven’t had a chance to try and fully replicate what I was experiencing previously but it seemed to help. Interestingly the jerky braking also seemed to get better initially but now is happening again. I’m considering just disconnecting the negative battery lead and leaving it overnight to get a fresh full reset and see if that helps. Sorry to hear you are experiencing similar issues.

 

[Royalstorm]

Back to the braking issue. I’ve isolated it to the car engine braking from 4th to 3rd gear. Even when switching to manual gate, when driving at a higher speed and then begin braking, the deceleration is fairly uniform until I downshift from 4th to 3rd. It then acts like the clutch is almost slipping and I lose the engine braking completely for a split second until the gear catches and then it decelerates again. Should I request that the dealer take a closer look at the transmission? It’s incredible annoying and frankly disconcerting to brake and actually have the car accelerate briefly before the engine reengages.